Tank assembly and related method of manufacture

ABSTRACT

A tank assembly having an elongated plastic tubular pipe structure and at least one end wall attached to the plastic tubular pipe structure and sized to cover a cross-sectional area defined by the plastic tubular pipe structure. The end wall is a composite unit including a first plastic sheet member having an edge portion and a second plastic sheet member bonded with the edge portion of the first plastic sheet member. The first plastic sheet member is located inward of the second plastic sheet member, the second plastic sheet member having a body portion with an outwardly domed shape to define an internal space between the body portion and a body portion of the first plastic sheet member. A structural foam is disposed in the internal space to provide continuity between the first plastic sheet member and the second plastic sheet member.

REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application No. 61/656,667, filed on Jun. 7, 2012, which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present application relates to a tank assembly and method for producing the tank assembly.

BACKGROUND

Tanks of various types are well known. Production of tanks utilizing a tubular pipe for the body of the tank is also known. For example, International Application No. PCT/FI2003/000631 discloses waste water tanks utilizing a tubular pipe body formed by spirally winding a thermoplastic profile. U.S. Patent Publication No. 2012/0097590 also discloses water tanks formed of tubular pipe formed by spiral winding of a composite profile. One issue faced in the production of such tanks, particularly when the tank will be buried in use, is providing end wall structures of sufficient strength and manufacturability.

It would be desirable to provide a tank assembly structure and method that is both efficient and economical in terms of end wall configuration and installation.

SUMMARY

In one aspect, a tank assembly is disclosed having an elongated plastic tubular pipe structure and at least one end wall attached to the plastic tubular pipe structure and sized to cover a cross-sectional area defined by the plastic tubular pipe structure. The end wall is a composite unit including a first plastic sheet member having an edge portion and a second plastic sheet member bonded with the edge portion of the first plastic sheet member. The first plastic sheet member is located inward of the second plastic sheet member, the second plastic sheet member having a body portion with an outwardly domed shape to define an internal space between the body portion and a body portion of the first plastic sheet member. A structural foam is disposed in the internal space to provide continuity between the first plastic sheet member and the second plastic sheet member.

In another aspect, a tank assembly is disclosed having an elongated plastic tubular pipe structure and at least one end wall attached to the plastic tubular pipe structure. The end wall is a composite unit including a first plastic sheet member sized to cover a cross-sectional area defined by the plastic tubular pipe structure, the first plastic sheet member bonded to the plastic tubular pipe structure, and a second plastic sheet member sized to cover the cross-sectional area and spaced apart from the first plastic sheet member to define a space therebetween, the second plastic sheet member bonded to the plastic tubular pipe structure. A structural foam is disposed in the space to provide continuity between the first plastic sheet member and the second plastic sheet member.

In another aspect, a method of manufacturing a tank assembly is disclosed, the method including the steps of joining an edge portion of a first plastic sheet member to a second plastic sheet member, where the second plastic sheet member includes a body portion that is domed outwardly away from a body portion of the first plastic sheet member to define an internal space therebetween, injecting an expanding structural foam into the internal space to fill the internal space once cured and provide continuity between the first plastic sheet member and the second plastic sheet member, and attaching the joined first plastic sheet member and second plastic sheet member to a tubular plastic pipe structure to block a passage through the tubular plastic pipe structure.

In yet another aspect, a method of manufacturing a tank assembly is disclosed, the method including the steps of joining an edge portion of a first plastic sheet member to a plastic tubular pipe structure to block a passage through the plastic tubular pipe structure joining an edge portion of a second plastic sheet member to the plastic tubular pipe structure to block the passage through the plastic tubular pipe structure, the second plastic sheet member spaced from the first plastic sheet member to define a space therebetween, and injecting an expanding structural foam into the space to fill the space once cured and provide continuity between the first plastic sheet member and the second plastic sheet member.

Other aspects of the disclosed device and method will become apparent from the following description, the accompanying drawings, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is longitudinal cross-sectional view of one embodiment of a tank assembly.

FIG. 2 is a longitudinal cross-sectional view of another embodiment of a tank assembly.

FIG. 3 is a longitudinal cross-sectional view of an additional embodiment of a tank assembly.

DETAILED DESCRIPTION

In an embodiment shown in FIG. 1, a tank assembly 10 includes an elongated plastic tubular pipe structure 12 and an end wall 14 attached to an end 11 of the plastic tubular pipe structure 12 to seal a passage 13 therethrough.

In the illustrated embodiment, the pipe structure 12 is a steel reinforced polyethylene pipe structure such as that shown and described in U.S. Pat. No. 7,004,202, which is formed by helically winding an elongated composite strip that includes a plastic base portion 16 and a plurality of ribs 18 that include a metal reinforcement 20 encased in plastic. The exact number and size of the ribs could vary. Moreover, the tubular pipe structure 12 could be of other configurations, such as solid wall HDPE pipe, dual wall HDPE pipe, corrugated plastic pipe, or a pipe formed of other plastic materials. Although U.S. Pat. No. 7,004,202 and FIG. 3 focus on the use of a metal reinforcement that is in flat strip form, other types of metal reinforcement are possible, such as the wire-type metal reinforcement of U.S. Pat. No. 7,975,728, where inboard and outboard reinforcement members are provided in the rib. Another alternative would be the use of a reinforcement such as that shown in U.S. Patent Publication No. 2009/0117302 where, in one example, the metal reinforcement has an inverted U-shape or V-shape with sidewardly extending feet encased within plastic that forms a hollow rib as opposed to a solid rib. The disclosures of U.S. Pat. Nos. 7,004,202 and 7,975,728, and U.S. Patent Publication No. 2009/0117302 are hereby incorporated by reference in their entireties.

The illustrated end wall 14 is structured as a composite unit formed in part by an inner plastic sheet member 22 sized to cover a transverse cross-sectional area defined by the plastic tubular pipe structure 12. An outer plastic sheet member 24 has an edge portion 26 bonded with an edge portion 28 of the inner plastic sheet member 22. The outer plastic sheet member 24 has a body portion 30 with an outwardly domed shape to define an internal space 32 between the body portion and a body portion 34 of the inner plastic sheet member 22. A structural foam 36 is disposed in the internal space 32 to provide continuity between the inner plastic sheet member 22 and the outer plastic sheet member 24.

In one embodiment, the outer plastic sheet member 24 may be vacuum formed into the dome shape prior to attaching outer sheet member 24 to the inner sheet member 22. However, the shape could also be achieved by molding or other means. Although the inner sheet member 22 is shown as generally flat or planar, such sheet member could likewise be curved or domed.

In one embodiment, both the inner plastic sheet member and the outer plastic sheet member are formed of HDPE material. However, it is recognized that other plastic materials could be used.

In one embodiment, the structural foam is an expanding urethane foam material. However, it is recognized that other structural foam materials could be used.

A thickness T22 of the inner plastic sheet member 22 may be between about 30 mils and 1,000 mils, and a thickness T24 of the outer plastic sheet member may also be between about 30 mils and 1000 mils. A thickness T36 of the structural foam 36 measured along a central longitudinal axis 38 of the plastic tubular pipe structure may be between about 1,000 mils and about 45,000 mils (i.e., about 1 inch to about 45 inches). In one implementation, plastic sheet thickness T22 and thickness T24 are each between about 150 mils and 800 mils, and foam thickness T36 is between about 5,000 mils and 30,000 mils. In one example, the overall thickness of the composite end wall (e.g., at its thickest point if thickness varies) is between about 10,000 mils and 30,000 mils (i.e., between about 10 and thirty inches).

In some embodiments, the structural foam thickness may be related to the overall diameter of the end wall structure. For example, in one implementation, where the diameter of the end wall is between about 48 inches and about 72 inches, the plastic sheet thickness T22 and thickness T24 are each between about 150 mils and 800 mils, and foam thickness T36 is between about 5,000 mils and 25,000 mils. In another implementation, where the diameter of the end wall is between about 72 inches and about 150 inches, the plastic sheet thickness T22 and thickness T24 are each between about 150 mils and 800 mils, and foam thickness T36 is between about 20,000 mils and 45,000 mils.

In one embodiment, the edge portion 26 of the outer plastic sheet member 24 is electrofusion welded to the edge portion 28 of the inner plastic sheet member 22, and the end wall 14 itself is electrofusion welded to the end 11 of the plastic tubular pipe structure 12. However, it is recognized that other connecting systems could be used, such as adhesives, chemical welds, conventional fusion welding using a heating process, or even mechanical fasteners.

A method of manufacturing the tank assembly 10 involves joining the edge portion 28 of inner plastic sheet member 22 to edge portion 26 of outer plastic sheet member 24 (e.g. via electrofusion welding or other technique such as conventional fusion welding), such that the internal space 32 is initially empty. An expanding structural foam 36 is then injected into the internal space 32 to fill the internal space 32 once cured. The joined plastic sheet members 22, 24 are attached to the end 11 of the tubular plastic pipe structure 12 to block the passage 13 through the tubular plastic pipe structure 12. In one example, the injecting step takes place prior to the attaching step, but the foam injection could take place after attachment to the pipe structure 12.

In general, electrofusion welding of pieces is achieved by placing electrofusion cord in contact with both pieces to be welded (e.g., both of the sheet members 22 and 24), and passing electrical current through the electrofusion cord to fusion weld plastic of the pieces together.

In one implementation the composite end wall structure is sized to be welded to the tubular end face 15 of the pipe structure 12 such that the dome of the end wall 14 fully protrudes beyond the end 11 of the pipe structure 12. In another implementation (as shown), the composite end wall structure 14 is sized to fit within the inner circumference 17 of the end 11 of the pipe structure 12, such that a peripheral edge 19 of the end wall 14 can be welded to the inwardly facing surface of the pipe wall 12 (inner circumference 17). The peripheral edge 19 of the end wall 14 may be the edge portion 26 of the outer plastic sheet member 24 or, alternately, the circumferential edge 28 of the inner plastic sheet member 22. In one example of the latter implementation, the domed portion of the end wall 14 protrudes partly from the end 11 of the pipe 12, but in another implementation the end wall 14 is positioned far enough within the pipe 12 such that the domed portion is flush with or slightly inward of the end 11 of the pipe 12.

Referring now to FIG. 2, a second embodiment of a tank assembly 10′ is shown. It is recognized that the tank assembly end wall 14 could be formed with one or more passages 40, 42 therethrough, which could be used for inlet and outlet of fluids from the tank assembly 10′ (e.g., via pipes connected thereto). Such passages 40, 42 could be formed before or after the end wall 14 is fixed to the pipe structure 12.

Referring now to FIG. 3, another embodiment of a tank assembly 50 is shown that includes an elongated plastic tubular pipe structure 52 with a passage 53 therethrough and an end wall 54 attached to the plastic tubular pipe structure 52 to block the passage 53, the end wall 54 being a composite unit formed in part by an inner plastic sheet member 56 sized to cover a transverse cross-sectional area defined by the plastic tubular pipe structure 52 and bonded to the plastic tubular pipe structure 52. An outer plastic sheet member 58 of the end wall 54 is also sized to cover the transverse cross-sectional area and is spaced apart from the inner plastic sheet member 56 to define a space 60 therebetween, the outer plastic sheet member 58 also bonded to the plastic tubular pipe structure 52. The outer plastic sheet member 58 may alternately be bonded to either an inner circumferential edge 64 of the elongated plastic tubular pipe structure 52 or a tubular end face 66 of the pipe structure 52. A structural foam 62 is disposed in the space to provide continuity between the sheet members. Unlike in the arrangement of FIG. 1, in the embodiment of FIG. 3, the edge portions 68, 70 of the two sheet members 56, 58 are not joined directly together. However, the edge portion 68, 70 of each plastic sheet member 56, 58 is joined (e.g., electrofusion welded or conventionally welded) to the plastic tubular pipe structure 52. Generally, the plastic sheet thickness and foam thickness of such an embodiment may be consistent with that described above.

A method of manufacturing the tank assembly of FIG. 3 involves joining an edge portion 68 of the inner plastic sheet member 56 to the plastic tubular pipe structure 52 to block the passage 53 through the plastic tubular pipe structure 52; joining an edge portion 70 of the outer plastic sheet member 58 to the plastic tubular pipe structure 52 to block the passage 53 through the plastic tubular pipe structure 52, the inner plastic sheet member 56 spaced from the outer plastic sheet member 58 to define a space 60 therebetween; and injecting an expanding structural foam 62 into the space 60 to fill the space once cured and provide continuity between the plastic sheet members 56, 58.

The generally flat composite wall structure of FIG. 3 could also be utilized as an internal wall (e.g., where the peripheral edge of the wall is welded to the inwardly facing surface of the pipe) to divide the pipe into distinct internal volumes. Also, one or more passages 40, 42 (FIG. 2) may be formed through the end wall 54 in the embodiment of FIG. 3.

It is to be clearly understood that the above description is intended by way of illustration and example only, is not intended to be taken by way of limitation, and that other changes and modifications are possible. The present application includes such changes and modifications and is limited only by the scope of the claims. 

What is claimed is:
 1. A tank assembly, comprising: an elongated plastic tubular pipe structure; at least one end wall attached to the plastic tubular pipe structure and sized to cover a cross-sectional area defined by the plastic tubular pipe structure, the end wall comprising a composite unit formed by: a first plastic sheet member having an edge portion; a second plastic sheet member bonded with the edge portion of the first plastic sheet member, the first plastic sheet member located inward of the second plastic sheet member, the second plastic sheet member having a body portion with an outwardly domed shape to define an internal space between the body portion and a body portion of the first plastic sheet member; a structural foam disposed in the internal space to provide continuity between the first plastic sheet member and the second plastic sheet member.
 2. The tank assembly of claim 1 wherein the second plastic sheet member has an edge portion, and the edge portion of the second plastic sheet member is bonded with the edge portion of the first plastic sheet member
 3. The tank assembly of claim 1 wherein: the elongated tubular pipe structure comprises an HDPE pipe; the first plastic sheet member is formed of HDPE material; the second plastic sheet member is formed of HDPE material; and the structural foam is an expanding foam urethane material.
 4. The tank assembly of claim 1 wherein: a thickness of the first plastic sheet member is between about 30 mils and 1,000 mils; a thickness of the second plastic sheet member is between about 30 mils and 1,000 mils; an a thickness of the structural foam measured along a central longitudinal axis of the plastic tubular pipe structure is between about 1,000 mils and about 45,000 mils.
 5. The tank assembly of claim 4 wherein the second plastic sheet member is welded to the edge portion of the first plastic sheet member, and the end wall is welded to the plastic tubular pipe structure.
 6. The tank assembly of claim 1 wherein: a thickness of the first plastic sheet member is between about 150 mils and 800 mils; a thickness of the second plastic sheet member is between about 150 mils and 800 mils; an a thickness of the structural foam measured along a central longitudinal axis of the plastic tubular pipe structure is between about 5,000 mils and about 30,000 mils.
 7. A tank assembly, comprising: an elongated plastic tubular pipe structure; at least one end wall attached to the plastic tubular pipe structure, the end wall comprising a composite unit formed by: a first plastic sheet member sized to cover a cross-sectional area defined by the plastic tubular pipe structure, the first plastic sheet member bonded to the plastic tubular pipe structure; a second plastic sheet member sized to cover the cross-sectional area and spaced apart from the first plastic sheet member to define a space therebetween, the second plastic sheet member bonded to the plastic tubular pipe structure; a structural foam disposed in the space to provide continuity between the first plastic sheet member and the second plastic sheet member.
 8. The tank assembly of claim 7 wherein the edge portion of the first plastic sheet member is welded to plastic pipe structure, and the edge portion of the second plastic sheet member is welded to the plastic pipe structure.
 9. The tank assembly of claim 7 wherein the end wall defines an end of the tank assembly.
 10. The tank assembly of claim 7 wherein the end wall defines an internal wall of the tank assembly to divide the elongated plastic tubular pipe structure into distinct internal volumes.
 11. A method of manufacturing a tank assembly, the method comprising: joining an edge portion of a first plastic sheet member to a second plastic sheet member, where the second plastic sheet member includes a body portion that is domed outwardly away from a body portion of the first plastic sheet member to define an internal space therebetween; injecting an expanding structural foam into the internal space to fill the internal space once cured and provide continuity between the first plastic sheet member and the second plastic sheet member; attaching the joined first plastic sheet member and second plastic sheet member to a tubular plastic pipe structure to block a passage through the tubular plastic pipe structure.
 12. The method of claim 11 wherein the joining step involves joining the edge portion of the first plastic sheet member to an edge portion of the second plastic sheet member.
 13. The method of claim 11 wherein the injecting step takes place prior to the attaching step.
 14. The method of claim 11 wherein the joining step involves electrofusion welding the edge portion of the first plastic sheet member to the second plastic sheet member.
 15. The method of claim 14 wherein the attaching step involves electrofusion welding the joined first plastic sheet member and second plastic sheet member to the plastic tubular pipe.
 16. The method of claim 14 wherein the joining step involves placing electrofusion cord in contact with both the first plastic sheet member and the second plastic sheet member, and passing electrical current through the electrofusion cord to fusion weld plastic of the first plastic sheet member to plastic of the second plastic sheet member.
 17. The method of claim 11 wherein the joining step involves utilizing heat to weld the plastic sheet members together.
 18. A method of manufacturing a tank assembly, the method comprising: joining an edge portion of a first plastic sheet member to a plastic tubular pipe structure to block a passage through the plastic tubular pipe structure; joining an edge portion of a second plastic sheet member to the plastic tubular pipe structure to block the passage through the plastic tubular pipe structure, the second plastic sheet member spaced from the first plastic sheet member to define a space therebetween; injecting an expanding structural foam into the space to fill the space once cured and provide continuity between the first plastic sheet member and the second plastic sheet member.
 19. The method of claim 18 wherein the joining steps involve welding.
 20. The method of claim 19 wherein the welding involves one of electrofusion welding or heat welding. 